Neurons and Synaptic Transmission

• What is a neuron?


  Nerve cells that carry information throughout the body via electrical and chemical signals
• What are the three types of neurons?

  Sensory, relay, and motor neurons
• What is the structure of a neuron?

  • Dendrites: Receive signals
  • Nucleus: Processes signals
  • Axon: Transmits electrical impulses
  • Myelin sheath: Speeds up impulses
  • Axon button: Converts impulses to chemical signals
• How do dendrites function in a neuron?


  Dendrites receive signals from other neurons
• What happens to the electrical impulse as it travels through the neuron?

  The impulse passes through the nucleus and along the axon
• What role does the myelin sheath play in neuron function?


  The myelin sheath speeds up the electrical impulse
• What occurs at the axon button of a neuron?

  The electrical impulse is converted to chemical messengers
• What is the function of a sensory neuron?


  Carry messages from sensory receptors in the PNS to the CNS
• What is the role of a relay neuron?


  Carry messages within the CNS
• What is the function of a motor neuron?


  Carry messages from the CNS to effectors
• What is synaptic transmission?


  The process of transmitting messages from one neuron to another neuron
• What is a synapse?


  Area where two neurons become close enough to pass chemical signals
• What are the parts of a synapse?


  • Pre-synaptic neuron
  • Synaptic cleft
  • Post-synaptic neuron
• What happens when the pre-synaptic neuron is excited by an action potential?


  It causes vesicles to fuse with the membrane and release neurotransmitters
• What occurs when neurotransmitters bind to receptors on the post-synaptic neuron?


  They cause an action to happen in the post-synaptic neuron
• What happens to neurotransmitters after they bind to receptors?


  They either diffuse out or are taken back into the pre-synaptic neuron
• What is excitation in terms of neurotransmission?

  When the neurotransmitter increases the positive charge of the post-synaptic neuron
• What is the effect of excitation on neuron firing?


  It increases the likelihood that the neuron will fire
• What is inhibition in neurotransmission?


  When the neurotransmitter decreases the positive charge of the post-synaptic neuron
• What is the effect of inhibition on neuron firing?


  It decreases the likelihood that the neuron will fire
• What is summation in the context of neuron firing?


  • A neuron can receive both excitatory and inhibitory neurotransmitters simultaneously
  • The likelihood of firing is determined by the net effect of these inputs
  • If the net effect is inhibitory, the neuron is less likely to fire
  • If the net effect is excitatory, the neuron is more likely to fire